The LCD (Liquid Crystal Display) possesses advantages of thin body, power saving and no radiation to be widely used in many application scope. Most of the liquid crystal displays on the present market are back light type liquid crystal displays, which comprise a liquid crystal display panel and a back light module. The working principle of the liquid crystal display panel is to locate liquid crystal molecules between two parallel glass substrates, and a plurality of vertical and horizontal tiny electrical wires are between the two glass substrates. The light of back light module is reflected to generate images by applying driving voltages to control whether the liquid crystal molecules to be changed directions.
At present, the main structure of the LCD panel on the market is shown in FIG. 1, and comprises a backlight source 1, a light guide plate 2, a brightness enhancement film 3, a lower polarizer 4, a TFT substrate 5, a liquid crystal layer 6, a color filter 7, an upper polarizer 8 and a reflective sheet 9. The voltage applied to the liquid crystal layer is controlled for manipulating the rotations of the liquid crystal molecules. Thus, a small angle change occurs to the polarization direction of the linearly polarized light generated with the light emitted by the backlight passing through the lower polarizer. The light passes through the color filter and forms color of various colors. Because the polarization direction of the light and the transmission axis of the upper polarizer have different included angles, the intensity of the emitting light can be controlled to form the display image that we want.
However, in prior arts, the liquid crystal itself in the liquid crystal display does not illuminate and has to rely on the backlight to provide the light source. With some reasons that the orientations of the liquid crystal molecules cannot perfectly satisfy the design requirements, as showing the black image, the pixels cannot be completely off, and some light still exiting out from the panel, which results in that the contrast cannot be reduced and cannot satisfy the requirement of high quality from the consumers.